This invention relates to pipe or conduit connections, and more particularly to a screw thread for thin-walled tubing. We define the term "thin-walled" herein to describe tubing having a wall thickness less than about one twenty-sixth its outside diameter.
It is difficult to create adequate threaded connections between a low-modulus thin-walled tube and a mating article, particularly where the tube is internally threaded. Compared to standard tubing, thin-walled tubes stretch more diametrally, so that low-depth threads formed inside such a tube can ramp up and over mating external threads on the article, particularly when the tube is under substantial pressure, or when an axial force is applied to the tube. The difficulties are like those in obtaining a good connection between a water hose and its end fitting. As a consequence, adhesives, external clamps and other types of compression fittings are often used to secure thin-walled tubing.
From a manufacturing and assembly standpoint, it would be desirable to have a threaded connection for thin-walled tubing which could be relied on.